This invention relates generally as indicated to a finishing and abrasive tool and, more particularly, to an abrasive spinner or finishing star tool having enhanced flexibility and a longer useful life.
Squares, cross pads and stars, called spinners, are forms of abrasive tools and are special application abrasive tools used for a variety of purposes. Each uses rectangular or square pads or bundles of sand paper or abrasive cloth with the tool being mounted on an arbor going through the center. Square pads, for example, may be used for grinding or blending of corners or for spot facing. As the pad rotates, the corners wear down and the tool becomes round. They abrade or cut almost as fast as hard wheels, but are easier to control and are more suitable for certain surfaces and shapes.
Cross pads are used for grinding, polishing and deburring as well as spot facing. One application is the ends of tubes or holes, both inside and out, for bell-mouth configurations, and chamfering. Cross pads have a generally x-shape configuration and this allows the operator to see the work since it is not completely obscured by the tool.
A star, sometimes called a finishing star, is something of a combination of both usually made from several packs of square abrasive sheets which are offset from each other on the rotational axis of the tool. For example, a star may be formed of at least two outside packs of abrasive sheets and at least two inside packs, with the inside packs each aligned and the outside packs each aligned, but the inside and outside packs offset 45xc2x0. This produces an eight-pointed symmetrical star. Additional packs offset symmetrically may produce stars with more points. The packs are usually held together with a two-part coined or swaged hole forming fastener with internal threads.
One of the problems with such tools is maintaining the desired flexibility for conformance to the work, particularly edges, ridges or projections, while at the same time providing enough rigidity, cushion or backup to perform the work properly. Too much of either characteristic will considerably shorten the tool life. Accordingly, there is a need for such a tool having both characteristics and longer tool life.
A rotary abrasive tool in the form of a star utilizes angularly offset packs of abrasive sheets or sand paper with each sheet radially slit, but with discontinuous slits. The discontinuous radial slits keep the slits from forming separate fingers which might break off in use but provide the desired surface flexibility for proper work application. An internally threaded two-part fastener secures the packs together and forms the center arbor hole. The middle of the tool may be provided with a cloth-sisal quilt to provide both a cushioning backing, and serve as a device to retain coolant or buffing or abrading compound applied to the tool. The cloth-sisal quilt core comprises outer cloth layers sewn to a sisal core and is the same square or rectilinear shape as the abrasive sheet or sand paper packs. The components of the quilt may be joined with a variety of sewing patterns and the quilt may be subject to dip treatments to improve working characteristics and wear.
A tool may typically comprise at least an outer pack of three or more abrasive coated square sheets, at least an inner pack offset 45xc2x0 on the mandrel axis, the cloth-sisal core also offset 45xc2x0, another inner pack also offset 45xc2x0, and an opposite outer pack aligned with the original outer pack. Such a tool provides an eight-point star with each point formed by a projecting corner of the packs, as an equilateral triangle. Additional packs which are symmetrically offset may produce a star with more points. The abrasive on the sheets may face in or out, or in both directions in a variety of patterns. The tools may vary in size from a diameter of about two inches to a diameter of about eight inches or more. The tool has improved flexibility and work characteristics, and, importantly, a longer useful life.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.